Notwithstanding the significant drop in crude oil prices during 2014-15, the long term trend in fossil fuel prices is likely to increase due to diminishing global oil and gas reserves, alternative (preferably renewable) energy generation systems have become an increasingly significant topic of interest for countries around the world, particularly as fossil fuel production threatens to continue unabated. As a result, significant time, resources, and funding have been invested to research and develop alternative electrical energy generation systems utilizing such renewable sources as solar power, water flow, wind power and the like to supply ever-increasing amounts of energy. One relatively untapped renewable energy source receiving increased attention is the potential energy that might be harnessed from ocean movement, such as the potentially endless energy source inherent in the constant tidal, wave, and/or current flows of the ocean.
The potential for generating electrical energy from the action of ocean phenomena generally comes in three sources: ocean thermal power, wave power, and tidal power. Ocean thermal power generation takes advantage of the difference in temperature between cooler deep water and warmer surface water that becomes heated by the sun; that thermal differential is then used to operate a heat engine for generating electricity. Ocean thermal power generation, however, is expensive, has very low thermal efficiencies, and may require equipment that can be an eye sore if located near populated areas. Furthermore, ocean thermal power generation requires large temperature gradients or differentials to function adequately. In many areas of the ocean, the actual thermal differential is not large enough to generate significant amounts of electrical energy to meet demand.
Wave power generation takes advantage of the waves generated on the ocean surface when wind interacts at the free surface of the water. Wave power generation is, however, highly dependent on wavelength and thus only suitable to specific locations of the ocean where large wavelengths are present. Wave power is also unreliable because wave quality is irregular and difficult to forecast, leading to unreliable energy generation. Similar to ocean thermal power, wave power may cause noise or visual pollution if wave energy generators are located near a populated area.
Tidal power generation techniques are expected to take advantage of the differences in the surface level of an ocean or similar body of tidal water due to the gravitational effects of the moon. The vertical difference in the surface level during tidal changes represents potential energy that holds promise for electrical power generation, and is particularly desirable because it follows a relatively regular pattern. Technology using tidal action as a source for energy generation is still in its relative infancy. One known tidal energy generation system utilizes large turbines placed in tidal streams in order to take advantage of the flow of water during tidal changes. A tidal stream is a relatively fast-flowing body of water that is created by the rising and falling of the tide; the turbines are positioned to capture the horizontal flow of water and thereby generate electricity. The fast-flowing water is thus directed through the turbine, which rotates a shaft attached to a magnetic rotor that converts the mechanical energy into electrical energy. These turbines are relatively expensive and may also require significant maintenance over their lifetime, thus increasing operating costs.
Another known method of harnessing tidal energy involves the use of a barrage. A barrage is a large dam where water spills over the dam as the tide rises. The overflowing water may be passed through a turbine, which rotates a shaft attached to a magnetic rotor that converts the mechanical energy into electrical energy. This process of using a barrage suffers from similar downsides as the tidal stream process and is limited to areas where a dam may be constructed such as tidal rivers, bays, and estuaries.
Other known tidal energy systems require the construction and placement of machinery such as hydraulics and moveable tanks that extend far above the surface of the water, such as described in U.S. Pat. Nos. 5,426,332, 5,872,406, and U.S. Patent Application Publication No. 2013/0134714. As another example, a known tidal energy system may require the construction of a large reservoir on land that must be filled so that a large duct system may capture the flow of water, as described in U.S. Pat. No. 4,288,985. Such tidal energy systems require large structures that are built either above the water or on shore, requiring significant costs in engineering and land.
A need therefore exists for an efficient and cost-effective energy conversion/electrical power generation system that can harness the potential and kinetic energy of tidal action as the water level rises and falls and/or as the water ebbs and flows due to changing tidal action and produce electrical power for subsequent consumption.